In the manufacture of semiconductor devices and other products, ion implantation is used to dope semiconductor wafers, display panels, or other workpieces with impurities. Ion implanters or ion implantation systems treat a workpiece with an ion beam, to produce n or p-type doped regions or to form passivation layers in the workpiece. When used for doping semiconductors, the ion implantation system injects a selected ion species to produce the desired extrinsic material, wherein implanting ions generated from source materials such as antimony, arsenic or phosphorus results in n-type extrinsic material wafers, and implanting materials such as boron, gallium or indium creates p-type extrinsic material portions in a semiconductor wafer.
Ion beams employed in ion implantation systems typically have a smaller cross-sectional area than a substrate or wafer to be implanted. In order for the ion beam to completely cover the wafer, the ion beam and/or the wafer are moved relative to one another in order to scan the entire wafer surface. In one example, an ion beam is deflected so as to scan across a wafer, which is held in place. In another example, an ion beam remains fixed while a wafer is mechanically moved to allow the ion beam to scan across the wafer. In yet another example, the ion beam is scanned in a fast/horizontal direction while the wafer is mechanically moved in a slow/vertical direction.
Serial ion implantations generally operate on a single wafer at a time. Relative motion between an ion beam and wafer is effected, referred to as scanning, so that the ion beam traces a raster pattern on the wafer surface. Typically, there is an amount of overlap between adjacent scan lines to facilitate uniform implantation across the wafer/workpiece.
During ion implantation, variations in beam related characteristics, including pressure, contaminations, scanning, and the like can impact dosimetry and implantation uniformity. Relatively small changes (of 10% or less) in current can be helpful to compensate for these changes and can provide a more uniform implantation across a target workpiece.